B1098, do you consume caffeine? If you do have you ever tried to eliminate it from you diet?
All i can say is i've been through what your going through, no antihistimine have ever worked for me.
Last year I decided to quit caffeine for a while because i noticed i was consuming coffee and energy drinks constantly. after two weeks i noticed my CU symptoms slowly declining in severity. after a month they were gone.
Now when I have a red bull or 3 cups of coffee i will itch when i sweat, but only for 4-5 days afterwards. I have complete control of my CU, simply by controling my caffeine. (I cannot say im cured, because I can still itch when i sweat, by drinking caffeinated drinks)
Assuming caffeine is in your diet, try to quit or cut down your intake for a while, it wont cost anything, and may possibly work for you...